py: int: fix multiply

Author: ncw

py/int.go

@@ -310,7 +310,7 @@ func intMul(a, b Int) Object {
 	if a < 0 {
 		absA = -a
 	}
-	absB := a
+	absB := b
 	if b < 0 {
 		absB = -b
 	}

py/tests/int.py

@@ -204,6 +204,8 @@
 assert (-211632533027288521429006868069*-5653252500022028208) == 1196412146422513287446928630654295043023252490352
 assert (-2705655979939764051*498507611145963097629681977143) == -1348790099142561628919972802250477720678595086293
 assert (12870925392758904855337167358*-178373424945516810458926560056) == -2295831044524626990552921549255668683393970507650109852048
+assert 21*2432902008176640000 == 51090942171709440000
+assert 2432902008176640000*21 == 51090942171709440000
 
 def approxEqual(a, b):
     assert abs(a/b - 1) < 1E-15